Case Study: Astute Design of Park Lock Solenoid Using DuPont Resins, Eliminates Fasteners, Speeds Assembly
Delrin® acetal resin and Zytel® nylon resin work together in a design that allows rapid assembly and smooth operation.
Application Description
Mounted in a car's steering column, an electronic park lock solenoid (EPLS) prevents the ignition from being turned off unless the transmission is safely in the park position. When the ignition switch is on, the solenoid coil is de-energized and its spring-loaded steel armature pin engages the ignition lock. With the shifter in park, the coil is energized to retract the pin and allow the key to be turned off.
The EPLS has four parts molded from DuPont™ Delrin® acetal resin: an override arm, a case consisting of a base and cover, and a disk pressed on the armature pin to engage the override arm. The solenoid's coil bobbin is molded from glass-reinforced DuPont Zytel® brand nylon resin.
Materials Selected and Why
Delrin® acetal resin meets needs for:
- Toughness, resilience and strength,
- Lubricity
- Dimensional stability
- Smooth molded surfaces
For the bobbin, Zytel® nylon provides strength and toughness.
Benefits Gained
- Rapid assembly – Exploiting the toughness and resilience of Delrin® , the design eliminates fasteners. Two snap fits hold the base and cover together, and another retains the override arm and its positioning spring.
- Twist-on installation – Delrin® provides strength for locking tabs and precision molding for a boss that allow the EPLS to rotate into place in the steering column casting.
- Automated coil assembly – For the bobbin, glass-reinforced Zytel® provides the strength and toughness needed to stand up to automated winding and to retain pressed-in coil terminations.
- Smooth operation – The inherent lubricity and smooth molded surfaces of Delrin® allow the override arm to slide over integral features on the case. This is required to hold the arm in place and pressed against the disk on the armature pin.
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